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Tarp tie-out under just 2lb pressure?

I wrapped a 2lb bar-bell tight with some 1/8" shock cord, using up all the stretch in the wrap.

Then I measured off 8" from the knot, pinched, and lifted the bar-bell by the cord at the pinch. The 8" about doubled in length and was within a few inches of maximum extension as the bell lifted from the floor.

That implies that all the tension on the tie-out with a nearly stretched out 8" length of 1/8" shock cord tensioner isjust 2 lbs / 1 kg.

First, that hardly seems like cranking it down.

Second, should much more pressure be applied to the tie-outs, from heavier shock cord and stronger elastomers?

Third, is 400 lb breaking strength tie-out line excessive, in preparation for a load all night of just 0.5% of that?

Last edited by DemostiX; 05-10-2012 at 21:45.
Reason: re-describe proceedure

What would be the disadvantage of just using shock-cord as a guy-line?

Long quote from first post in this thread:

It should be noted that self tensioning guylines used with stakes is a loaded sling shot with a sharp projectile. Be careful and hold on to the stake when the self tensioning guyline is tensioned. I use stakes that have smooth round shafts and attach the stake to the guyline using a clove hitch because it is easy to tie with the two overlapping loop technique and the clove hitch knot will simply fall out when I slide it down and off the shaft of the smooth round stake. They also stay attached to the guyline until I slide them off; I personally feel it is safer that way. Be careful and set your stake firmly in the ground so that it doesn’t have a tendency to pull free and launch itself with the self tensioned guylines. The 3/32 inch and 1/8 inch shock cord isn’t particularly strong and you don’t have a long throw with the doubled over 12 inch piece so it shouldn’t be an accident waiting for a place to happen if you take reasonable precautions. I have done this without accident and without losing a stake for many years but I have heard of stakes being launched and lost as well as tarps torn and people getting minor injures from stakes attached to shock cord striking an arm or hand.

One should be particularly careful when removing tensioned stakes from the ground as they want to shoot towards the tarp like a sling shot and if you are bent down where your face is in range of the sling shot you are putting yourself in a bad position. That is probably your most vulnerable time, removing a tensioned stake from the ground. I try to keep one hand on the stake, one hand on the free end of the guyline, and stand on the safe side of the stake when I remove them… you are on the safe side when the stake is between you and the tarp. Always remember that the sling shot is pointed towards the tarp and it can’t get you if you keep the stake between you and the tarp. I keep that in mind and practice that religiously whether I am inserting a tensioned stake into the ground or removing it from the ground… you need to respect them as they can jump out and get you. If you are not comfortable dealing with tensioned guylines attached to a stake, you should not use them…you don’t have to have tensioned stakes to use tarps, they simply have some advantages in that they help keep a tarp taut without readjustments and less likely to droop, flap or get damaged in high winds.

I believe it's something to do with the richochet effect- this is lessened when you have a regular 'string' attached as well, and not as much shock cord tightened down. Shug uses shock cord for his pull outs (not tie outs) and that works well and is flexible.

Multipurpose shock cordage

Bicycle inner tubes from thin large bike tubes cut 1/2" wide are a very nice multipurpose item.
Cut pieces for shock cords.
Use long for lashings.
In a pinch they make great firestarter tinder that works when wet.
In a pinch they are good for a slingshot.
They make good grip wraps..
We cut rubber bands for altoid tins..etc..